And that's what I don't understand. Instructing a team of juniors works very well, in fact it has been the predominant way of making software for some time now. Hire a bit more junior than what you need, and work them a bit above their pay grade thanks to your experience. That's just business as usual.

So I guess what these studies show is that most engineers are not really good when it comes to piloting juniors, which has been a known fact forever. That's often cited as a reason why most seniors will never make it to staff level.